Jan. 5—Investigators identified the Pennsylvania man accused of killing four University of Idaho students with cell phone records, surveillance of his vehicle, DNA evidence found at the scene, and a DNA analysis of trash collected from his parents' home in Pennsylvania, according to court documents.

Idaho authorities unsealed the probable-cause affidavit for Bryan Kohberger's arrest on Thursday after his arrival in the state. Kohberger, 28, was arrested in Pennsylvania last Friday in connection with the November killings of Kaylee Goncalves, 21, of Rathdrum, Idaho; Madison Mogen, 21, of Coeur d'Alene, Idaho; Xana Kernodle, 20, of Post Falls, Idaho; and Ethan Chapin, 20, of Conway, Wash.

Kohberger made his first court appearance in Pennsylvania on Tuesday, where he waived his extradition hearing, prompting his return to Latah County, where the killings occurred. He appeared in Latah County Court for the first time Thursday.

Police began to zero in on Kohberger after finding a "tan leather knife sheath" at the scene next to Mogen, the affidavit says. Forensic analysts located a "single source of male DNA" on the sheath's button snap. Investigators later linked that DNA to Kohberger after analyzing trash taken from his parents' home in Albrightsville in Monroe County's Chestnuthill Township that contained the DNA of a male "as not being excluded as the biological father" of the person whose DNA was found at the scene.

"At least 99.998% of the male population would be expected to be excluded from the possibility of being the suspect's biological father," the affidavit reads.

A surviving roommate identified as D.M. told police that on Nov. 13, the night of the killings, she saw a man "clad in black clothing and a mask that covered the person's mouth and nose walking towards her." She described him as 5-foot-10 or taller, and "not very muscular, but athletically built with bushy eyebrows," according to the affidavit. Police say that Kohberger, at 6 feet tall and 185 pounds, matches that description.

After reviewing video footage in and around the neighborhood, authorities identified Kohberger's vehicle — a white 2015 Hyundai Elantra — in the area between 3:29 and 4:20 a.m. The vehicle made three passes by the scene before it entered the area a final time at 4:04, and was later captured leaving the area "at a high rate of speed."

The vehicle arrived back on the nearby campus of Washington State University, where Kohberger was a doctoral student in the school's criminal justice and criminology department, at about 5:25 a.m. Police believe the killings occurred between 4 and 4:25 a.m.

Police also tracked Kohberger's vehicle traveling across the country in mid-December, with license-plate readers in Colorado and Indiana capturing the car's tags. Surveillance video showed the car in Albrightsville as early as Dec. 16.

Cell phone records for a device registered to Kohberger matched the path of his vehicle on the night of the killings, the affidavit says. Police, however, were not able to track it to the car's path because it appeared to have been off for about two hours, which authorities said is "consistent with Kohberger attempting to conceal his location during the quadruple homicide."

Additionally, a review of cell phone records dating back to June showed a device registered to Kohberger near the crime scene at least a dozen times.

"All of these occasions, except for one, occurred in the late evening and early morning hours on their respective days," the affidavit reads.

Kohberger is being held without bail and could face the death penalty if convicted, the Moscow-Pullman Daily News reports.

Read the affidavit below:

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